Prior to the present invention, various one and two-package moisture curable room temperature vulcanizable (RTV) compositions were available based on the use of a silanol-terminated polydiorganosiloxane consisting essentially of from about 50 to about 2500 chemically combined units of the formula, ##STR1## where R is a C.sub.(1-13) monovalent substituted or unsubstituted hydrocarbon radical, which is preferably methyl, or a member selected from phenyl, cyanoethyl, trifluoropropyl, vinyl, and mixtures thereof. The silanol-terminated polydiorganosiloxane of formula (1) was generally mixed with a cross-linking silane having hydrolyzable radicals attached to silicon and a condensation catalyst, such as a tin compound or a titanium compound. In some instances undesirable by-products such as acetic acid, were formed as a result of the cure of the room temperature vulcanizable organopolysiloxane compositions which generated a disagreeable odor or which rendered the organopolysiloxane composition corrosive, or both.
The present invention is based on the discovery that substantially odor-free and non-corrosive one-package room temperature vulcanizable RTV compositions can be made by mixing together an effective amount of a vanadium compound defined hereinafter, with an alkoxysilane crosslinking agent having the formula, ##STR2## where R.sup.1 is a C.sub.(1-8) aliphatic organic radical selected from alkyl radicals, alkylether radicals, alkylester radicals, alkylketone radicals and alkylcyano or a C.sub.(7-13) aralkyl radical, R.sup.2 is a C.sub.(1-13) monovalent organic radical selected from R radicals as previously defined, and a is a whole number equal to 0 or 1, and a silanol-terminated polydiorganosiloxanes consisting essentially of chemically combined units of formula (1). Preferably, the vanadium compound utilized in the practice of the present invention has the formula, EQU VO(OR.sup.3).sub.3, (3)
where R.sup.3 is a member selected from the class consisting of a silyl radical and a C.sub.(1-13) organic radical. Unexpectedly, the vanadium compound provides (RTV) compositions having unusually fast tack-free times (in minutes) after accelerated aging, as compared to various RTV compositions of the prior art containing either a tin compound or titanium compound as a condensation catalyst.
The above results are also quite surprising in view of Lamoreaux U.S. Pat. No. 3,334,066 assigned to the same assignee as the present invention directed to a curable composition comprising a trialkoxy vanadate and a silanol-containing organopolysiloxane. Unlike the moisture curable compositions of the present invention utilizing an alkoxy silane cross-linking agent, the curable composition of Lamoreaux, are cured by application of heat. In some instances, separation of an organic solvent also has been found to facilitate cure in the practice of the Lamoreaux method.